We're obliged to all those readers who sent in suggestions as to just what El Reg's new Special Projects Bureau should be doing with its multi-billion pound budget and mountain fab bunker complex, and the first thing that caught our eye was the N-Prize – "a challenge to launch an impossibly small satellite into orbit on a …

So that's your acronym then.

Low Orbit Helium Assisted N-Winner

Although, 19.99g max? Don't know if you'd even be able to carry a battery into orbit, let alone anything else. Can you fit a solar cell, capacitor and a pulsing radio transmitter into a coin-sized container? And could you pick it up through all that atmosphere? How does anyone intend to prove 9 orbits with a payload that small?

19.99g

Sputnik-1 redux

Picking up a radio emitter is not a problem provided you know where to look. Think of radio-telescopes picking up emissions from other galaxies close to the edge of the observable universe. Compared to that, something emitting 100mW pulses from low orbit would be trivial.

Tracking the micro-sat from launch would be the tricky bit. Guiding it into any particular orbit harder still.

Another idea that might work is a lightweight corner-cube relector and an earth-based laser illuminator. After all, they measure the distance to the moon by laser-illuminating a corner-cube that the manned moon missions left behind! One for low earth orbit could be much smaller and lighter.

mass != weight

Detecting it from orbit

I imagine the laser reflector would be very hit and miss. But surely there are enough Radio Hams in the El Reg's audience that they could do some very-long base-line interferometry? Synchronisation could be fun, but not unachievable - if the frequencies are low enough.

top acronym

I was thinking on reading the article that if a helium balloon is too costly, why not make a hydrogen one? It's not like it's going to matter if it blows up. I reckon (in a totally non-numerical sense) a lacquered paper balloon could retain enough hydrogen to lift it quite a distance. You wouldn't necessarily need any expensive pressurised hydrogen tanks. If you had some sort of chemical or electrolytic reaction to produce the hydrogen and a way of sequestering at least some of the oxygen (in plain electrolysis of water) you could probably produce and trap enough of it in the balloon to get you to the desired height.

Once at a high enough altitude, you could then, hopefully, use a more conventional rocket to carry the payload beyond the atmosphere. Aiming would be tricky, but if you suspend the rocket below the hydrogen-producing part and have a combination of barometer (altimeter) and accelerometer readings (maybe combined with a timer) you can use a bit of fuzzy logic to determine the best time to engage the rocket stage while it's more or less pointing in the right direction and still retaining at least some kinetic energy from the balloon contraption.

Alternatively, I read that the most recent volcanic eruption in Iceland threw ash and other stuff up to a height of over 12 miles. That's still a long way to go to get to LEO and obviously reliant on the occurrence of a relatively rare event, not to mention needing to design a secondary rocket which could survive the initial lift-off, but at least it reduces the cost of the primary ballistic system to zero.

Hit and miss...

Indeed I wonder a bit about the regulation of this. Genuine request for information: what bureaucracy and red tape must one negotiate to get permission to attempt to put something into orbit? (esp. from the UK, although any illumination is welcome).

Balloon

A mylar balloon would be trackable in orbit and not need any batteries or solar cells - the two Echo passive communications satellites in the 1950s were nothing more than huge balloons that reflected radio waves.

Mylar Balloons

Possibly doable. According to the rules, the little sparklet bulb or whatever you're inflating the thing with needn't be part of the 19.99g payload either. So long as everything separates, I imagine you could pack quite a lot of mylar into just under 20g.

Another problem, even assuming you can build a rocket that can go from 0 to orbital velocity, and do so in a light enough package that a helium/hydrogen balloon can lift it up to the edge of the atmosphere, is guidance. I've seen a lot of comments on the N-Prize site to the effect of "oh just get the angle right and you're sorted", but I just can't see that happening without a just-suborbital projectile bouncing off the atmosphere like a skimming stone and losing precious speed through unintended aerobraking. That or ending up in a very highly elliptical orbit with a perigee of somewhere in the middle of the Pacific. For a bit of fun, download yourselves a copy of Orbiter (it's freeware, go google for it) and see what happens when you just point the Delta Glider "somewhere in that direction" and give it some welly without any control.

Also, doing this WITHOUT some kind of System On Board-derived guidance system just isn't geeky enough. You can fit a capable-enough computer into a SIM card these days and servos are nicely lightweight too. Solid state gyroes are relatively inexpensive and light enough. Horizon detection would be tricky but the hardware component is essentially an array of IR sensors and maybe a second SoB. You might also want to be able to keep the delivery vehicle stable enough to be able to fire a second stabilising burn halfway around before flinging your mylar jet-can out. You'd be pushing the bounds of the £999.99 budget, but so long as you can McGuyver a lot of ingredients it does only seem ALMOST impossible.

On a parting note, did the X-Prize lawyers seriously send one of their legal love letters to the N-Prize organiser?

Flammable hydrogen

Right, let's speculate!

You go up with the balloon, then want to use the gas for fuel. This will require several things. We need a balloon that can be deflated on command (plausible) , a controlled burn gaseous hydrogen rocket (difficult) and a main capsule that can control its orientation in the upper atmosphere.

Initial thoughts would be to launch the balloon up to a certain height, then force deflate it, compressing the gas internally within the main capsule. During this stage the craft will be in freefall, so the gas needs to be compressed as quickly as possible to minimise altitude loss. Problem: Heat from compressing the gas could lead to explosion, need study to find out how likely this is.

Once the hydrogen is compressed, we dump the balloon (with a parachute for recovery, balloons ain't cheap) align the main capsule and hit the burn button. This ignites our carefully released hydrogen fuel (some form of pulse rocket? Need to think about that.) and we burn for LEO. Do the rules specify what they're considering "space" to be? Anyway, once up, we release the satellite (Electronics chappies can probably do something with 20g) and hope it's somewhere vaguely stable for the next ~12 hours.

Recovery of the main capsule is a non-trivial problem left to the reader.

@mwk: compress the hydrogen slowly during ascent

High altitude baloons tend to start on the ground partially inflated, to allow for expansion as the air pressure and temperature drops with altitude. This is likely to result in accelerated lift, as the baloon expands in the thinning atmosphere. If you want to use the hydrogen in the baloon as the next stage rocket fuel, it seems to make sense to remove the hydrogen from the baloon gradually, compressing this for fuel in order to allow constant baloon size and lift. By the time you are at maximum altitude for baloon lift, it seems to make sense to discard the rest of the hydrogen and the baloon, which won't be very much fuel, rather than lose altitude while compressing the rest. Once you are at say 10% of atmospheric pressure you have compressed 90% of the hydrogen if you assume constant baloon volume. This approach is assisted by the fact that the higher the altitude the lower the temperature, so the temperature increase resulting from compression of the fuel is less likely to result in hydrogen explosion.

The problem with the rocket then is likely to be getting enough oxygen from the depleted atmosphere at 10% atmospheric pressure. Having to carry some or all of the oxygen up increases the cost and payload needed at rocket launch time.

@mwh

You'd want to check the availability of the other component required for burning: our old friend O2, aka oxygen. I gather there's not much of it to be had at the height rocoons split (taking PARIS' maximum altitude as a guideline).

I doubt aiming for using the hydrogen for a bit of extra boost would be even marginally worthwhile..

I have no idea what I'm talking about here but just thinking out loud

Any chance you could pack a battery, pump, logic/control system and compression tank into that weight limit to regulate the altitude and keep it at trade wind height?

...or maybe just leak it out (no pump, no tank) to an acceptable (if that's even possible, see below*) pressure once it gets to the proper height?

Just thinking about the Japanese Ballon Bombs in WWII - from http://en.wikipedia.org/wiki/Fire_balloon :

* "A hydrogen balloon expands when warmed by the sunlight, and rises; then it contracts when cooled at night, and falls. The engineers devised a control system driven by an altimeter to discard ballast. When the balloon descended below 9 km (30,000 ft), it electrically fired a charge to cut loose sandbags. The sandbags were carried on a cast-aluminium four-spoked wheel and discarded two at a time to keep the wheel balanced.[3]

Similarly, when the balloon rose above about 11.6 km (38,000 ft), the altimeter activated a valve to vent hydrogen. The hydrogen was also vented if the balloon's pressure reached a critical level.[3]"

@AC 06:48

There's no need to regulate altitude; you want the balloon to go as high as it can without bursting, and that last bit can be delayed by venting gas as the balloon expands. At some point the buoyancy will become neutral, which is when you want to fire the rocket.

Helium too pricey?

... then use hydrogen instead and shoot for the non-reusable category surely? Assuming you would need about 40(?) moles of hydrogen (half a cubic metre at stp), that would require a bit over 2.5kWh of electricity to generate. I guess you would collect the gas directly in the balloon somehow to save costs which would mean pressurising the vessel you do the electrolysis in slightly. If you could sustain 100W it would be filled in about 4 days, assuming you don't loose too much gas by leakage through the balloon skin.

Slight correction

I was thinking this too

It's not like you benefit from lack of flammability in Helium given that you have a rocket strapped to it. Perhaps there would be a way to harness the Hydrogen as extra fuel or blow the balloon up to provide an initial boost to the rocket. In fact it would be fair to say that there is NO WAY this could POSSIBLY go wrong.

Social engineering is the way forward.

Given the budget & realism restraints, and with a tenous link to the IT context, I guess social engineering is the most probable path to success.

You know, make small package of appropriately camouflaged material, sneak into an ESA/NASA cleanroom (or the Chinese, Indian or Russian equivalents) and stick it in a bigger satellite that has an appropriate flight plan.

Sadly the prize money will be eaten for breakfast by the ensuing lawyering.

Rockoon - Helium??

Why expensive helium?

Hydrogen is much cheaper. Given that the cargo is potentially explosive anyway, the balloon fairly small and probably destined for one-off use, surely hydrogen.

For a micro-satellite, launch at high altitude (as high as possible) has huge advantages. Fuel scales as size cubed, whereas air drag scales as size squared, so the smaller the rocket, the more it's going to lose to drag and the greater the advantage of launching with most of the atmosphere beneath it.

I bought two meteo balloons for €5

They were KAYSAM 300 gramme helium balloon, (a single one ascends at about 320 metres per minute to deflate at around 10 millibar atmospheric pressure or 25 kilometres altitude). If everything else is equally sourced from the ham-radio fleamarket route then you could emulate the initial Galileo frequency claim satellite which seemed to be an 'iPod fused with a Nokia Phone' rather than space qualified components.

I think I WOULD like to wear a tin-hat should large numbers of N-prize attempts start to be made!

Not obviously impossible

Low Earth orbit is around 10km/s which for a 10g payload is only a megajoule of energy, so at current prices you could do it for well under a pound.

However, I think most of the rockets that have made it into space have delivered a payload two or three orders of magnitude smaller than the delivery vehicle. On the face of it then, your energy costs alone are going to blow the budget even if the whole of the rest of the system is re-usable.

So we can expect that a winning entry will have to recover some of this energy, perhaps by sticking a large windmill out of its window on re-entry.

Yes!!

I was thinking along those lines. I would use a hydrogen baloon, to lift a rocket as high as it would go. Sticking out of the nose of the rocket, there would be a high-velocity rifle. The rifle would fire as the rocket reaches max height. Now, I haven't decided yet, if the projectile needs to be another, much smaller barrel, I should probably do some tests or calculations or something. Or not.